Automotive companies are requiring paint suppliers to meet stricter specifications involving paint cleanliness, color, cost and delivery schedule as they face increasingly stringent quality requirements in the marketplace. Consumers are demanding greater durability and color in the automotive finishes. At the same time, government regulations are becoming more demanding of reductions in airborne emissions. Consequently, waterborne and high solids paint formulations are becoming increasingly more important.
The conventional paint manufacturing process consists of mixing or blending resins, solvents, intermediates and millbases in large tanks with slow paddle mixers. This process is especially efficient for low-solid, solvent-based finishes since the high solvent content in these formulations allows for a wide compatibility among the various ingredients.
In high solid and waterborne formulations, on the other hand, there is little solvent present to compatabilize the various ingredients. Additionally, water borne formulations contain high levels of expensive, hydrophobic, and hard-to-grind pigments. In addition, these formulations tend to higher viscosities, making the conventional manufacturing process of large tanks and paddle mixers inefficient and slow.
In addition, high solids or waterborne paint formulations present another manufacturing difficulty. Typically these formulations contain high levels of materials having an extremely narrow compatibility tolerances. Pigment "shocking" and "kickout," whereby components separate into separate phases within the mixing vessel, often results from localized incompatibility within the confinement of a mixing tank. Furthermore, millbase made at high solids and low solvent levels often flocculate when its incorporation into the mixture is slow. The resulting floculated mixture is "milky" in color with reduced pigment efficiency.
To overcome these formulating problems, difficult-to-incorporate materials are made into compatible mixtures off-line as intermediates and are combined together in a series of steps to make a finished product. These additional mixing steps consume time and money. In addition, each intermediate step increases loss of raw materials as well as the possibility of decreased quality as intermediates are transferred from tank to tank.